Field of the Invention
The invention relates to a folder having at least one folding unit including at least two mutually cooperating product-carrying cylinders, the folder having further folding attachments, and devices for increasing cutting accuracy.
The prior art, as exemplified by the published German Patent Document DE 39 32 931 A1, discloses a folding jaw cylinder formed, between adjacent folding jaws thereof, with flats or cavities closable, if necessary, by elastic coverings. The cavities are arranged in a manner that, when folding bars and grooved bars, respectively, pass through the nip between the puncturing and folding knife cylinder and the folding jaw cylinder, the cavities are located opposite the bars. Consequently, so to speak, a widening of the nip occurs, so that any occurring stoppages or blockages and any paper accumulations, respectively, can pass through the nip between the cylinders, without either of the cylinders being damaged thereby. At the remaining circumferential regions, an enlargement of the nip is made possible by the fact that adjusting devices are guided in eccentrically mounted pins. In the case of a paper jam, these segments are thus able to yield. Also in the region of the grooved bars and cutting bars, respectively, a widening of the nip is achieved by the respective flats or cavities when the bars pass through the nip.
German Patent 671 790 is concerned with a cutting and collecting device for rotary printing presses. At a collecting cylinder, three grooved bars located on the latter can be continuously and automatically displaced alternatingly forward and backward, respectively, in the circumferential direction in accordance with the changing positions of cutting lines of respective cutting knives. Through this solution, the grooved bars can be adjusted so that they coincide with the respective cutting line of the cutting knives. Consequently, both the wear on the grooved bars can be reduced and the accuracy of the cutting operation can be increased.
In the case wherein the folders, respectively, have two folding units disposed, for example, above one another, wherein an incoming material web can undergo a longitudinal cut or wherein a plurality of material webs can run in, a partial web or entire material web to be fed to the lower folding unit follows a relatively long path, as a result of which, because of a deflection at a plurality of rollers, web tension fluctuations may result, which can lead to an inaccurate, namely slit-like, execution of the punctures, and which, in addition, are accompanied by an inaccurate cutting operation when respective copies are severed from the partial web or from the entire material web. Because of the relatively long transport path leading to the lower folding unit, losses in quality with respect to cutting accuracy and folding position of the folded copies produced by the lower folding unit can result.